In a general heat exchanger, as shown in FIG. 1, a heat exchanger fin 3 is attached to an external side of a metallic heat exchanger tube including a refrigerant inlet pipe 1 and a refrigerant outlet pipe 2 to improve heat transfer, and a header made of a metallic material is coupled to left and right sides of the metallic heat exchanger tube to fix the heat exchanger. The heat exchanger is made of an expensive metallic material such as aluminum alloy, copper and the like and fabricated through complicated processes, thereby increasing fabrication time and cost. Thus, it is difficult to mass-produce the heat exchanger.
Meanwhile, in order to solve the problem, there was proposed a joint method between a tube and a tube header for a plastic heat exchanger (Korean Patent No. 10-0366430), in which the heat exchanger was made of a plastic material and the tube and header were fused to each other by an inverted triangular mold using heat fusion. However, in this method, because the tube and header are not fused integrally to each other with deformation of their original shapes, but simply joined by heat of the mode using heat fusion, it is difficult to maintain airtightness of refrigerant which is essentially required in the heat exchanger, and thus because it is impossible to maintain a refrigerant pressure of a condenser in a refrigeration cycle and also the refrigeration cycle is not formed normally, thereby deteriorating performance of the heat exchanger.